Apparatus for forming molds for inlays and crowns



F. s. MEYER June 4, 1929.

APPARATUS FOR FORMING MOLDS FOR INLAYS AND CROWNS Filed July 2, 1927 Patented June 4, 1929.

FREDERICK s. MEYER, or MINNEAPOLIS, lv runnsome.

-APPARATUS non FORMING ivronns Fort INLAYS "Ann citovvns."

" npplication'filed July 2, 1927. Serial naaeazar.

This invention relates to dental apparatus for-casting inlays and crowns and especially to apparatus for preparing and forming the mold. I v

'In carrying out the usual process for forming the casting mold for inlays or crowns. the wax model is first carefully prepared and attached to the end of a sprue orpin; The

sprue with the model'thereon is next mount- H vtionable in forming lmolds for the smaller ed in upstanding position'upon a crucible former in axial ahnement therewlth and a so-called investment ring IS'COHIIQCtQd 1th said crucible former surrounding'thewax model, and forming in conjunction with said crucible former an investment container.

The container so formed is filled with the I chine a relatively larger sprue apertur-e'is desir'ablef in the mold to ins'urethe properpassage of'gold than when casting with the presinvestmcntcompound in plastic semi-liquid condition and the investment 13 permitted to set or-harden with the wax model'disposed' therein. The-elimination of thewaX model from the mold is then necessary to complete the preparation of the mold.

I have developed, through extensive ex perimental work, a technique for investing the wax model which -overcomes to a large extent, the distortion of the wax model and which further overcomes or compensates for 1 shrinkage of the gold in the process of casting, 'A highly efiicient apparatus is neces-.

sary tosucc'essfully carry out my technique and itii s, therefore, the main object of this invention to provide simple but highly ef'- ficient apparatus,including av crucible former, s'prue and investmentring, the combination. 'co-operation and co-actlon thereof when used in connection with mytechnique producing a nearly perfect mold for the casting of an inlay or crown.

The container formed by the usual invest ment ring and crucible former is filled with the investmentccompoun din semi-fluid state,

said compound being mixed with, a substantial amount of water; In the'standard rings and will be apparent from" the following descrip- I *tion made in conneotion vvith the accompanyi ng drawings in Which'jlike reference,

crucible formers now in use the ring loosely always small amounts of water escape from between the bottom of thering and said crucible former. The slightest escape of vvater therefrom causes the investment compound to settle towards the bottom, tending to cause a distortion of the wax model.

It is, therefore,a further object of my in- 1 pound.

nection to formj'the investmentcontainer, and

. further capable :When so joined of being lifted or carried as one unit without displacement I of the investment material When-in fluid state: i

and withoutdistortion of the wax :model disposed therein. I 1

.Sprues used heretofore have been objec inlays due to the :fact'that the'model will usually be slightly distorted atthe time the heated spine is inserted'therein, the slightest tilting of the heated sprue relatively to the model causing the distortion. In casting in lays'or crowns withacentrifugal casting masurie casting machine. Consequently, agsprue of substantial, diameter mustbe used in prechincsand heretofore spruesof substantially adjustable in diameter to meet the requirei paring moldsafor the use in centrifugal mas;

. uniform diameter. throughout have been uti-" lized with imperfect results in the; forming a of the smaller castings. objectiof my I mentsv foreithe r a centrifugal or pressure i type of casting inachln'e and furthermore capable of effecting a relatively .large'sprueaperture in the mold without occasioningthe objectionable distortion above described. 1 A further object of my invention is to .pro

vide an investment ring adapted tobeedetachably connected'to a crucible former with a water tight joint therebetween and further having means adapted to retain the invest Y ment compound and lessen the tendencytherof to settle during the setting of said com- These and 'other objects of the invention charactei'srefer to similar parts throughout the'several views, and niwhiohr Fig; lisa side elevation of my apparatus fassembled witli'theinvestment ring and-mold shownin cross'section;

Figiflis a cross sectionshovving the greater part of my crucible former in plan and taken on the line 2-2 of Fig. 3;

Fig.3 isanaxial vertical section of my crucible formerhaving a portion of the inshoulder 7 otconsiderable height. Groove vcstment ring in connection therewith;

Fig. 4 is a side elevation of my Crucible former having the ax model mounted there,-

on by means'of my improved sprue is a n udina s e ien 9 9 form of my investment ring; r

r Fig. 6 is a cross sectionof my investment ring With the mold formed therein, taken on the line 6'6 of Fig. 1; Fig. 7 is alongitudinal section of my preterred form of sprue detachedjand F ig 8 is'a longitnc linalsejction of; slightly difterentembodiment of investment ring than that shown in Fig. 5. 1 it M y3mproved crucible former comprises. a

/ luomember or disc 7 havin an axiall dis- P h. c

posed convert stud 7 A concentric groove 7 surrounds stud 7, said groove being defined-on its inner side by a tapered annular 7 isfilled withsome plastic sealing substance such asparaflin or beeswax, the purpose of which willlater beexplained. I g

Athreaded socket-is provided in crucible former 7 extending axially" thereof and through-aconsiderable portion of stud 7? and Iprovide a small sprue chuck 8 threadedly engaging said socket'and having a longitudinal ly split inner end terminating in a conical extremity 8? adapted to contact the trim catedconical end of said socket,fthe longitudinal inWard-inovement of chuck 8 Within said socket. causing the split innerf end tobe adapted tofbe adjustabl-y. slidable 'one Within the other. As. illustrated, an outer tubular section 9?" of. approximately the. diameter of:

contracted to clamp the. sprue therein.

V Myimproved-sprue comprises. a plurality of. telescoped sections: (preferably three.)-

. relatively heavy sprues now in use is provided- 7' 7 oi the crucible. former, or if desired, the

having. telescoped therein an intermediate tubular; section 9 vvhich telescopically car- I ries the model pin 9;" Aslshowmthe several sections 9%, 9?? andf'9. are of equal length, and

preferably are of; substantially thehei'ght of ;my crucible formercfrom. the base tothe apex ot the :stud. Obviously, alllof the sections may be projected above; the, apex of; the stud:

pin 9 may be alone projected to produce a relatively. small sprne hole in the mold, or if desired,'either. or bothoithe tubularsec tions may be projected for. some distance above'theapex of the stud 7. and pin 9 projectedf a relatively. short distance above the. 2

upper end of saidtubularmembers toengage, the, model Pin 9. preferably has anengagement end: of? square cross section adapted; to.

engage the model. Theseyeral sections of I my sprue fittight ly and. maybe slidably ad- .justed and obviouslymay be employed v or not the chuck 8 is used. 7 is used the outer tubular section 9 mayv be j connection With a crucible former Whether If the chuck 8 outwardly projecti g corrugation, also numbered as 10 since there 'Will be no tendency to in any Way weakenzthe', intermediate po'r 7 tion of the mold Whenthatstructure is usedJ,

Investment ring 10 isof the same diameter at each end and either end may be snugly tele-. scoped over the tapered. annular shoulder 7 ofmycrucibleformer, the peripheral edgeof i the engaging end being disposed Wi groove 7 and its connection With crucible former. 7 sealed by means of; the beeswax or 1 other'plastic material X groove.

' T e l ter Y indicates a; We model, disposed on my sprue, 9- havinga relatively dense inner investment Zthereon. I

In preparing a'mold, for cast1 ng,:the Wax end of my sprne 9?. Tubular sprue member 19 is then mounted Within the sprue chuck 8 a being. inserted fromthe upper; stud end of the crucible former. and; is secured in proper position relative to stud '7. The desired section ofthe sprue is projected the properd-istance from above the apex. 0t stud 7?, the

square, engagement end of pint) having'been,

Wax model Ifa'relatively large sprue aperdisposed within said model is first obtained and placed upon the it of cou se, first heated and inserted'into the ture; connecting with the mold "is desired;

one. of the. larger. sections of the spine is projected; from the apex of stud; 7 into close relation atits upper end withthe' Wax model}, 7 ,1

My inyestment ring 10 is then telescoped at one, end over. shoulder 7 the edge thereoffbeing, tightly. sealed by means of the tapered shoulder and material X disposed within roo lpre f m a r e ve y lense Y inner investment Z about my wax model be.-.-

fore filling, the investment ring with iii-yestmentmaterial. My technique for the investme'nt is of considerable 'importance'but will 11. 9 1 6 described here as the process constitutes no partot this invention. The in-" vestment ring isnextffi lled a warmine vestment compoundgM; and the crucible form peraturetocausea certain expansion of the .Wax model to compensate for the shrinkage of the goldcasting. Atterithe. investment is .120 er-gand. ring, connected therewithare prefer J ably disposed in an oven at the. proper tem set thecrucibie former-f 7 may, otfcourse, be. I

remm edv and; with it, the sprue and tubular member, said spree leaving in said mold an aperture communicatingwith theWax model. It will be seen that myyinvestment ring will be snugly connected with my crucible former, a water tight joint being interposed therebetween, due to the plastic material within groove 7 and the tapered annular shoulder 7 The'joined members constituting theinvestnient container may be handled or moved as a unit without danger of displacing the parts, and there will be no leakage between the investment ring and'crucible former andconsequently no settling of the investment compound to distort the model.

The circumferential bead or corrugation in the medial portion of the investment ring prevents displacement of the mold when heat is applied to the ring. Such displacement often occurred with rings heretofore utilized.

The functions and advantages of my improved sprue are probably clear from the foregoing description. utilized to form passages in the mold of three different diameters and further will prevent or minimize the distortion of the wax model when the pin is inserted, due to the fact that engagement is made with the small pin '9, evenwhen one of the larger tubular sections are used to form the sprue hole in the mold.

It is of great importance to adjust the sprue properly relative to the crucible former and l'O'llOlCl the same firm against displacement. This I may accomplish by the use of a simple but highly eiiicient chuck axially disposed with crucible former 7.

From the foregoing description it will be seen that I have invented, after extensive experimental work, highly efiicient apparatus for forming molds for the casting of inlays and crowns, said apparatus being adapted .to greatly lessen the damage of distortion of the waxmodel.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of the invention.

What is claimed is:

V 1. Apparatus for forming a mold for inlays 0 r crowns comprising an investment ring and a crucible former having an upstanding stud adapted to axially retain a sprue former, said crucible former having a tapered upstanding shoulder about which one end of said investment ring is adapted tosnugly telescope to secure said parts together, said crucibleformeralso having a groove enc1r-' cling said shoulder in which one edge of said investment ring is adapted to be seated.

'2. Apparatus for forming a mold for inlays or crowns comprising an investment ring and a crucible former having an upstanding stud adapted toaxially retain a sprue former, said crucible former having a groove surrounding said stud in which one end of said investment ring is adapted to be seated, and

My sprue may be a lillliig' Of plastic material in said groove adapted to-form a seal between said crucible former andsaid investment ring and adapted moreover to secure said parts together 1 3. Apparatus for forming a mold for inlays or crowns conip'rising a crucible former having a convexupstanding stud and means for connectionwith an investment ring, said stud being provided with a threaded axial) socket extending from the base of said crucible former to a medial portion thereof and terminating in a tapered seat, a chuck having engagement withsaid threaded-socket and provided with a split inner end, and terminating in a tapered portion adapted to engage said tapered seat, and a sprue telescoped within said chuck and projecting normally beyond the apex of said stud.

4. Apparatus for forming ainold for inlays or crowns comprising a crucible former adapted to be connected with an investment ring and having anupstanding stud thereon, said studhaving an axial port therethrough, and a sprue former comprising a tubular member telescoped within said port andea pin of smaller diameter telescoped within said tubular member and longitudinally slidable therein. V

5. In apparatus for forming a, mold for inlays'or crowns, a sprue adapted to be adjustably connected to a crucible former,com-' prising a plurality of telescoped sections, said inner section comprising a pin of relatively small diameter adapted toengage and retain the plastic model.

6. In apparatus for forming a mold for inlays or crowns, a crucible former comprising a body having a substantially annular shoul der about'which an investment ring is adapted to be positioned, said body also having a groove encircling said shoulder in which one ed e of said investment ring is adapted to'be V seated and retained. V 7 In apparatus for adapted to carry a sprue former, said body forming a mold for illlays, a crucible formercomprising a'body' having an annular groove in which oneend of an investment ring is adaptedtobe' seated I and a filling'of plastic material in said groove adapted to form a seal between said body and an investment ring and adapted moreover to secure said parts together.

8., In apparatus for forming a mold for inlays or crowns, an investment ring adapted to be connected with a crucible former com prising a tubular body havi'ng an outwardly pro ectin g circumferentially disposed bulge adapted to prevent displacement ofaj mold therein, said bulge causing an enlarged por 'tlOIl to be formed in said mold between'the ends thereof.

,9. In apparatus of the class described, f

investment ring liavingan annular edge at one end thereof and a closure for said end having an annular groove therein in which one end thereof and a closure member for said the annular edge of salcl lnvestment ring is endhaving a tapered annular shoulder about adapted to bes'eated, and a filling. of plastic which said edge of said investment ring is 10 material in said groove adapted to forin'a adapted to snugly telescope to tightly secure 7 '5 seal between said edge ands'aid closure. said ring and closure together.

10. In apparatus of the class described, an In testimony vvliereofI afix my signature/. investment ring having an annular edge'at FREDERICK S. MEYER. 

